It is known to employ electrolytes for the deposition of gold electrodeposits, U.S. Pat. Nos. 2,967,135, 2,905,601, 3,149,057 3,303,112 and 3,598,706, which are incorporated herein by reference. Frequently, hardeners such as cobalt, nickel, silver and copper are codeposited with the gold.
There have been several disadvantages with the plating solutions used in the past. Firstly, the content of the codeposit hardener is erratic. This means that the plated surfaces have different abrasion and wear characteristics from batch to batch. Secondly, the previously used electrolytes have poor throwing power when there is an acceptable cathode deposition rate, i.e., 30 mg/amp min or more. This results in more gold being used than the theoretical amount required to obtain a minimum thickness of gold on the most shielded part of the cathodic surface.